Free flight arming device



May 9, 1961 J. RABINOW FREE FLIGHT ARMING DEVICE Original Filed July 5,1956 3 Sheets-Sheet 1 4 la l 16 .m M MD TN 1 N J E h M a R m @1 W x J JB 4 M 5% @J a w 7 May 9, 1961 J. RABINOW FREE FLIGHT ARMING DEVICEOriginal Filed July 5, 1956 3 Sheets-Sheet 2 /6 gum INVENTOR.

By Jacob R ahinn'Lu.

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J. RABINOW FREE FLIGHT ARMING DEVICE Original Filed July 5, 1956 May 9,1961 3 Sheets-Sheet 3 INVENTOR. Jana]: Rahinum.

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Patented May 9,- 1961 FREE FLIGHT ARMING DEVICE Jacob Rabinow, PrinceGeorges County, Md., assignor to the United States of America asrepresented by the Secretary of the Army Original application July 5,1956, Ser. No. 596,118,

new Patent No. 2,938,461, dated May 31, 1960. Divided and thisapplication Sept. 4, 1958, Ser. No. 769,273

4 Claims. (Cl. 200-6145) (Granted under Title 35, U.S. Code (1952), see.266) The invention described herein may be manufactured or used by orfor the Government for governmental purposes without the payment to meof any royalty thereon. This application is a division of applicationSer. No. 596,118, filed July 5, 1956.

This invention pertains to the art of fuzing projectiles such as bombs,rockets, mortar shells and others. More particularly it relates tosafety and arming systems for projectiles. In projectiles" of this type,particularly in the case of bombs, the arming cycle of a fuze is usuallystarted by the withdrawal of an arming wire or the charging of acapacitor at the instant of bomb release. Serious accidents haveoccurred in the past because of the fact that bombs have beenaccidentally dropped onto airfield runways or decks of aircraftcarriers. In such cases the fuzes generally complete their arming cycleeven though substantial air travel is normally required. The backwash ofpropellers or of turbo-jet engines operates arming vanes of such fuzesand duplicates the conditions encountered in proper drops. In some fuzesprovision is made to sterilize the fuze if impact occurs before properarming in order to avoid this disadvantage. This leads to other troublessince such sterilization schemes may result in duds. For example, a bombmay jostle another bomb accidentally immediately after release or a bombmay hit a part of the bomb bay upon its release from the aircraft andthus cause a dud.

To eliminate these disadvantages and to insure much greater safety, thepresent invention comprises an arming system which makes use of the factthat a bomb or other low velocity projectile in free flight experiencesacceleration of less than 1 g. I make use of this fact by a special zerog device so connected that the bomb must be in free flight for severalseconds for arming to occur. If the bomb employing this invention shouldaccidentally fall upon the deck of a carrier or upon an airfield runwayit would not arm because it then would be under acceleration of 1 g orgreater. As described more fully herein, the device can be so arrangedthat accidental jostling of one bomb by another will not permanentlydisarm the bomb and proper function will result. This invention ofarming a bomb or other projectile under conditions of zero-g orfractional-g may be employed in either electrical or mechanical form.

One object of this invention, therefore, is an arming system for fuzesadapted to remain inoperative in the event the containing projectile isaccidentally dropped upon an airfield runway or aircraft carrier deck.

Another object is an arming system adapted to remain inoperative in theevent the fuze is subjected to an acceleration greater than apredetermined amount occurring subsequent to the expiration of apredetermined time.

A further object is a fuze arming system as aforesaid which will armeven though subjected to an excessively great acceleration provided thatacceleration occurs prior to the expiration of a predetermined timeinterval.

A still further object is a safety device for fuze arming systemsadapted to prevent fuze arming in the event the containing missile isaccidentally dropped upon an airfield or aircraft carrier runway.

The specific nature of the invention as well as other objects andadvantages thereof will clearly appear from the following descriptionand accompanying drawings in which:

Figure 1 is a vertical sectional view of one form of my safety switch inthe normal condition.

Figure 2 is a cross sectional view of the device of Fig.

' 1 taken on the lines 2-2 thereof.

Figure 3 shows the switch of Fig. 1 in the actuated condition.

Figure 4 is a view similar to Fig. 2 showing the switch in the actuatedcondition.

Figure 5 is a vertical sectional view of a second form of my switch inthe normal condition.

Figure 6 shows the switch of Fig. 5 in the actuated condition.

Figure 7 is a schematic view of an unarmed fuze embodying the armingsystem of this invention.

Figure 8 is a fragmentary view of Fig. 7 showing the fuze in the armedcondition. I

Figure 9 is a schematic diagram of the electrical circuitry of the fuzeshown in Fig. 7.

Figure 10 is a variation of the circuit of Fig. 9.

Figure 11 is a schematic view of a mechanical switch which is theequivalent of the electrical switch of Fig. 5.

Figure 12 shows the switch of Fig. 11 in the actuated condition.

Referring now to Fig. 1, a metal electrical conductive housing 1supports an insulating member 2 within the hollow base 2a thereof.Afiixed to member 2 centrally thereof and extending upwardly therefromis terminal 3. A helical spring 4 has its inner end afiixed to terminal3, the outer end of spring 4 having affixed thereto a heavy metal ring'5, the ring being concentric with terminal 3 and normally out ofcontact with all members other than spring 4. Housing 1 is perforated atTia and 1b to prevent electrical contact between housing 1 and terminal3.

Fig. 3 shows the contact established between ring 5 and housing 1 whenthe fuze is under an acceleration of one g or greater acting in adirection upwardly along the surface of the drawing. If one leg of anelectrical circuit, not shown in this figure, terminates at housing 1and the other leg terminates at terminal 3, the circuit will becompleted through spring 4 and ring 5 under the condition described.

Figure 4 shows that electrical contact is made under sidewiseacceleration (as compared to the upward acceleration of Fig. 3). Ring 5now contacts the side, rather than the base, of housing 1.

Referring to Fig. 5, a generally cylindrical housing 6 supports aninsulating disc 7 which is provided with a cup-like recess 7a in whichrests a cylindrical Weight 8 axially bored at one end. A tension spring9 maintains the weight normally in central position by having one endthereof afiixed to disc 7 centrally thereof and the other end affixed tothe closed end of weight 8.

Fig. 6 shows the action which takes place when the assembly of Fig. 5 isaccelerated substantially at a right angle to the axis of the weight 8.Spring 9 is extended by the force exerted upon it by weight 8, theweight being permitted to pivot sidewise on its base and in so doing tocontact housing 6. Thus, a circuit is completed through spring 9 andweight 8 when terminated at spring 9 and housing 6.

While one device such as shown in Figs. 5 and vdis.

cessive acceleration regardless of the direction of the.

acceleration.

Referring now to Fig. 7, a fuze ogive has mounted upon it a contact ring11, insulated from the ogive by a suitable member 12, and connected bywiring 13 to a power supply 14, the power supply being grounded to theogive. Power supply 14, in turn, is connected to anacceleration-sensitive switch 15. The switch'15 maybe of a type shown inFigs. 1 or 5. Switch 15 is also connected with the heating element 16 ofan explosive motor 16a which, when activated, will cause the expansionof bellows member 16b. The bellows member is so positioned thatexpansion thereof will cause linear motion of the safety block 17' untilthat motion is arrested by the stop 18. When such motion has occurred,explosive detonator 19 in aperture 19a of block 17 will be aligned withaperture 20 in safety plate 21, permitting ignition of the boostercharge 22 when firing pin 23, which is normally biased forwardly byspring 24, is caused to move rearwardly and engage detonator 19 as aresult of impact of pin 23 with a target, not shown. The armed positionof explosive motor 16a and block 17 is shown in Figure 8.

The electrical circuitry of the system of Fig. 8. as shown in Fig. 9employs a capacitor 25, one plate of which is grounded to fuze ogive 10and the other plate of which is connected with contact ring 11. A secondcapacitor 26 has one plate connected to ground and the other plateconnected through a resistor 27 with contact ring 11. Heating element 16of explosive motor 16a is connected in series with diode 28 and thesetwo elements are connected in parallel with capacitor 26. Safetyswitches 29 and 29a, which are identical in construction, but whose axesare oriented mutually perpendicular, are connected in parallel and thecombination connected in parallel with capacitor 26. A resistor 30 maybe connected in series with the switches 29 and 29a.

The circuitry of Fig. 10 is a modification of that shown in Fig. 9. Thesystem of Fig. 10 contains its own power supply 31 which is substitutedfor capacitor in Fig. 9.

Safety device 32, shown here in block form, must be placed in serieswith power supply 31, such as a battery, to prevent the fuze frombecoming energized prematurely. Device 32 may be operated by theconventional arming wire or any other suitable arming device as known tothe art. Contact ring 11 is not required when a self-contained powersupply is employed inasmuch as the purpose of the ring is to collect acharge from an external source. A resistor may or may not be employed inseries with switches 29 and 29a for reasons discussed hereinafter.

Referring again to Fig. 9, as fuze ogive 10 and ring 11 are brought intocontact with the terminals of a voltage source, not shown, uponlaunching, a charge is placed upon capacitor 25. This charge leaks tocapacitor 26 through resistor 27 until the striking voltage of diode 28has been reached. Upon the attainment of such voltage, diode 28 fires,causing current to flow through heating element 16 of explosive motor16a. If, however, either of the switches 2) or 29a should close beforefiring of the diode 28 occurs, capacitor 26 will discharge through theswitch circuit so completed. The time required for capacitor 26 toassume its initial charge, to discharge through one or the other ofswitches 29, 29a, and to recharge from capacitor 25 after suchdischarge, is determined by the values of resistor 27 and capacitor 25,by the voltage on capacitor 25 and by any charge which remains uponcapacitor 26 afterthe switch reopens. The charge which remains uponcapacitor 26, for a given capacitor and voltage, is determined by theduration of closure of switches 29 or 29a, up to complete discharge, andby the resistance of the circuit, which may be increased by the additionof a resistor 30 in series with the devices 29 and 29a.

The operation of the circuit of Fig. 10 is identical with the operationof the circuit of. Fig. 9 with the exception that power in the Fig. 10circuit is made available to charge capacitor 26 through resistor 27from power supply 31 upon actuation of safety device 32 whereas in theFig. 9 circuit capacitor 26 is charged through resistor 27 fromcapacitor 25 after capacitor 25 has collected a charge from an externalsource when the projectile is launched.

Now it can be seen that,"should a bomb containing a fuze such as thatshown in Fig. 7, strike the bomb bay of the airplane upon beingreleased, a part, at least, of the charge upon capacitor 26 will bedischarged through one of the switches 29, 29a, which switch was causedto' close under an impact of the bomb with the bomb bay. The amount ofcharge upon capacitor 26 is small at this time inasmuch as the bomb wasreleased only moments before the impact occurred. Sulficient chargeremains upon capacitor 25 to recharge capacitor 26 after the switchreopens after the bomb moves clear of the airplane. Thus, the fuze is.in condition to'function properly upon impact with a targetlater in itsflight.

If, however, the bomb should fall upon an airfield runway or upon thedeck of an aircraft carrier as the plane is ascending or descending,there is a different result. One of the switches 29,29a'wi1l close asbefore. The

chargeupon capacitor 26 will discharge through the closed switch asbefore. This time, however, capacitor 26 will have drawn from capacitor25 an amount of charge short of that required to fire diode 28 but sufficient to prevent capacitor 25 from recharging capacitor 26 after theswitch reopens upon the abatement of acceleration of 1 g or greater. Thefuze will, therefore, remain inoperative and safe.

Referring now to Fig. 11, it will be seen that a great similarity existsto the configuration of the device shown in Fig. 5 in that a cylindricalhousing 6a is provided with a base 7b having a cup-like recess 70 inwhich rests a cylindrical weight 8a axially bored at one end. A tensionspring 9a, one end of which is aflixed to base 7b and the other end ofwhich is aflixed to the closed end of weight 8a, normally maintains theweight in the central position shown in Fig. 11. 'In this embodiment,however, it is not necessary that the housing 6a or the weight 8a beconductive, nor that the base 7b be nonconductive, inasmuch as thisdevice operates upon me chanical rather than electrical principles. Theweight 8a is connected to a lever 33, pivoted at 33a, by means of amotion transmitting linkage 34, such as a cord or cable, threadedthrough an aperture 38 provided therefor in base 7b. A detent 33b isprovided at one end of lever 33 to engage a tooth 35 on balancewheel 36of a clock type arming system, not shown.

In Fig. 12 the device is shown being acted upon by an acceleration of 1g or greater directed generally perpendicular to the axis of weight 8a.Weight 8a is driven sidewise by this force and in so doing extends thespring 911. It also exerts a pull upon linkage 34 which is caused tomove to the right of the drawing; Lever 33 is caused to rotatecounterclockwise about pivot 33a so that detent 33b engages tooth 35 andarrests the motion of balancewheel 36. during the time the fuzeissubject to an acceleration of at least 1 g.

It will be understood that the embodiments described herein areexemplary only and that other modifications may be made withoutdeparting from the spirit and scope of the invention as set forth in theclaims.

What I claim is: v

1. An acceleration sensitive switch comprising a hollow generallycylindrical electrically conductive housing havsaid housing, said coilspring having the inner end there-' of afixed to saidterminal andextending radially therefrom, a heavy conductive ring afiixedto andsupported by In this manner fuze arming is delayed the outer end of saidspring normally out of contact with said housing and acting as the firstswitch contact, said housing serving as the second switch contact, saidring being movable laterally of said housing with said spring to engagein uninsulated portion of said housing and complete an electricalcircuit through the switch when said switch is subjected to anacceleration greater than a predetermined amount.

2. An acceleration sensitive switch comprising a hollow generallycylindrical electrically conductive housing having a base comprising agenerally disc-shaped insulating member, a generally cup shapedelectrically conductive weight arranged coaxially in said housing, saidweight having the open end thereof normally resting upon said insulatingmember, a tension spring enclosed within said weight and having one endaflixed to said insulating member and the other end aifixed to theclosed end of said cup shaped weight remote from said insulating member,said housing serving as the first switch contact and said weight servingas the second switch contact, said weight pivoting upon said insulatingmember so that the spring connected end of said weight contacts anuninsulated portion of said housing to complete an electrical circuitthrough said switch when the switch is References Cited in the file ofthis patent UNITED STATES PATENTS 1,055,153 Ferguson Mar. 4, 19132,311,637 Buchanan Feb. 23, 1943 2,317,982 Diehl May 4, 1943 2,671,832Hansard et al. Mar. 9, 1954 FOREIGN PATENTS 468,169 Great Britain June30, 1937 303,312 Switzerland Feb. 1, 1955

